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West Elk Mine <br />1) Verification and Accuracy of Predictions <br />In order to verify and demonstrate the accuracy of subsidence predictions, based on the results of past <br />subsidence observations in the Apache Rocks and Box Canyon mining areas, MCC will implement the <br />following procedures to monitor Monument Dam prior to mining. The following procedures will be <br />implemented as soon as permitting allows, in order to account for seasonal precipitation changes. <br />1. Conduct annual aerial photo surveys of the landslides located north and south of the reservoir, <br />using the July 2004 photos as a baseline reference. Surveys will continue while mining is <br />occurring within Panels EI through E9 <br />2. Install, and measure, survey monuments strategically located on the dam and on the north, south, <br />and east edges of the reservoir to monitor any movement prior to, during, and after mining in the <br />area. During the monument surveys, conduct visual inspections along the monument transects for <br />surface cracks. Monitoring (surveying and inspections) of stations in the Minnesota Reservoir <br />area and across the crest of the Monument Dam will be initiated at least one month prior to <br />mining of Panel E12 or E-1 and continue for two to three months after mining is complete in the <br />panel. MCC will initially survey the monuments on the dam axis quarterly and then monthly <br />when E -seam longwall mining is occurring within one mile of the dam. The results of the <br />surveys will be submitted in the semi-annual subsidence reports. While mining is occurring <br />within the one mile radius, weekly inspections will be made of the dam for cracks or other <br />potentially damaging features and the inspection reports will be included with the semi-annual <br />subsidence reports. The monuments along the dam and reservoir basin will be resurveyed as soon <br />as possible if a seismic event occurs that exceeds the "threshold event" as described below. If, <br />during the inspections, cracks or other potentially damaging features are noted to be occurring in <br />the reservoir basin or dam structure, CDMG, the Minnesota Reservoir Company, SEO, USFS and <br />other -'appropriate agencies will be notified by MCC immediately and, depending on the severity <br />of the dainage, mining may cease until a new mine plan can be approved and mitigation <br />performed. <br />In addition to the survey monuments on the dam, MCC will measure the water level in the <br />piezometers installed in the crest of the dam on monthly basis, April through October, when <br />accessible. The water level measurements will be included in the semi-annual subsidence reports. <br />Mining of Panel E9 will be from the south to the north. Monitoring (surveying) of stations to the <br />south of the Minnesota Reservoir and across the crest of the Monument Dam will be re-initiated <br />at least one month prior to mining of Panel E9 and continue for two to three months after mining <br />is complete in the panel. MCC will initially survey the monuments on the dam axis quarterly and <br />then monthly when E -seam longwall mining is occurring within one mile of the dam. The results <br />of the surveys will be submitted in the semi-annual subsidence reports. While mining is <br />occurring within the one mile radius, weekly inspections will be made of the darn for cracks or <br />other potentially damaging features and the inspection reports will be included with the semi- <br />annual subsidence <br />reports. The monuments along the dam and reservoir basin v.-', 11 resurveyed as soon as possible <br />if a seismic event occurs that exceeds the "threshold event" as described below. If, during the <br />inspections. cracks or other potentially damaging features are noted to be occurring in the <br />reservoir basin or dam structure, CD1\4G; the Minnesota Reservoir Company; SEO, USFS and <br />other appropriate agencies will be notified by MCC immediately and, depending on the severity <br />40 damage, the damage, mining may cease until a new mine plan can be approved and mitigation <br />performed. <br />2.O5-166 Revised June 2005 PRIO, Rev. March 2006; A1ay 2006 PRIO, Nov. 2006TR107..4pri12007TR108;Sep. 2007 PR12; Feb. 2008 PR -12 <br />